Accumulating live roller conveyor

ABSTRACT

Several groups of transport rollers and a depressible sensing roller (between every two adjacent groups) of transport rollers constitute an article supporting bed of the conveyor, which bed is divided into a plurality of successive zones each containing one group of transport rollers and one sensing roller. A plurality of driving belts constantly engage the group of transport rollers in the respective zones, and separate driving means independently propel the several driving belts from a common drive source. Each zone is provided with control means, responsive to depression of the sensing roller in that zone by passage of an article thereover, to disengage the driving means of the driving belt in the next preceding zone until the depressed sensing roller in the following zone is raised after passage of the article thereover.

United States Patent [191 Sadler, Jr.

[ Feb. 13, 1973 1 ACCUMULATING LIVE ROLLER CONVEYOR [76] Inventor:Albert Corneil Sadler, ,]r., 147

Primary Examiner-Richard E. Aegerter Attorney-Fetherstonhaugh & Co.

[ 5 7 ABSTRACT Several groups of transport rollers and a depressiblesensing roller (between every two adjacent groups) of transport rollersconstitutean article supporting bed of the conveyor, which bed isdivided into a plurality of successive zones each/containing one groupof transport rollers and one se'nsing roller. A plurality of drivingbelts constantly engage the group of transport rollers in the respectivezones, and separate driving means independently propelthe severaldriving belts from a common drive source. Each zone is provided withcontrol means, responsive to depression of the sensing roller in thatzoneby passage of an article thereover, to disengage the driving meansof the driving belt in the next preceding zone until the depressedsensing roller in the following zone is raised after passage of thearticle thereover.

14 Claims, 6 Drawing Figures Z-2 ONE ZONE Z/ Z-:?

sum 10F 2 INVENTOR Albert Corneil SADLER, .IR.

PA TENT AGENTS av? aw mvv mm kw imh aak mm mm Q L 9 Q N\ ww PATENTEDFEB13 I973 \N MZON M20 PATENTEDFEBIBMS 3.716.129

SHEET 2 OF 2 INVENTOR Alba" Corneil SADLERJR.

- PATENT ENTS ACCUMULATING LIVE ROLLER CONVEYOR This invention relatesto new and useful improvements in live roller conveyors, andparticularly the invention concerns itself with live roller conveyors ofthe so-called accumulating type.

In live roller conveyors the article transporting rollers arepower-driven, and it often happens that the passage of an article alongthe conveyor is stopped, either accidentally by some obstruction orpurposely as for example when the article arrives at some work stationwhere temporary stoppage of the article is necessary in order to performsome type of work thereon.

In conventional practice, even a temporary stoppage of an article on alive roller conveyor has resulted in the piping up or accumulation ofsubsequent articles against the stopped article, and this has producednot only an undesirable congestion at the work station or at the pointof blockage, but also an excessive drag on the propelling mechanism ofthe conveyor, thus causing premature wear and unnecessary breakdowns inoperation as well as damage to the conveyed item.

In recognition of these difficulties, the prior art has endeavored toprovide live roller conveyors of the socalled accumulating type in whichthe article supporting and transporting bed of the conveyor is dividedinto a plurality of successive zones and means are provided in each zonefor sensing the passage of an article therethrough and de-activating thepower drive of the next preceding zone so that until an article haspassed through one zone, a subsequent article cannot pass through thepreceding zone. This arrangement works out remarkably well in that itaffords an intermittent flow of articles in spaced apart relation alongthe conveyor and thus prevents piling up of articles against one whichhas been accidentally or purposely stopped. In other words, although theconveyor is live or power driven, in the event of an article stoppagethe de-activation of one or more of the conveyor zones facilitatesaccumulation of several articles on the conveyor in spaced apartrelation and at a standstill, until the stopped article has resumed itsmovement. In this context the conveyor is of the accumulating type, asalready noted.

The live rollers of the conveyor are usually driven by an endless beltwhich engages the underside of the rollers, and in conventionalaccumulating type of conveyors as outlined above, the practice has beento provide means for disengaging the driving belt from the rollers inone zone so as to de-activate such rollers until an article has passedover the sensing roller in the next following or downstream" zone. Inthe meantime the driving belt must actuate the transport rollers in allzones except those in the zone which has been stopped. As a practicalmatter, each zone may have a length of 2 or 3 feet and may contain six,nine or more transport rollers. The driving belt spans the several zonesof the conveyor, so in each zone, in accordance with conventionalpractice, it is necessary to bring a 2 or 3 foot length of the belt indriving engagement with six, nine or more of the rollers in that zoneand, conversely, to disengage that length of the belt from that manyrollers when the flow of an article through that zone is to be stopped.This presents many difficulties in that complicated and expensive meanshave to be utilized for shifting the driving belt in and out ofengagement with the rollers in the respective groups, and even when thatis accomplished with reasonable satisfaction, the action is notnecessarily uniform with varying sized packages and becomes more complexas the package shapes and weight range' 'increase. The first attemptedsolution of this problem was to mount the rollers supporting the maindrive belt on pivots and to cause the package weight to pivot therollers and thus the belt out of drive engagement. The means used tohold the rollers and belt in drive was either a spring or acounterweight. The force exerted by this means governed the drive forceon the conveyor, however, it also governed the weight required to sensethe package presence. In practice it is necessary to set the system tohandle the heaviest packages (maximum spring force) and consequentlylighter packages would hang up on the sensing roller (unable to depress)and/or would develop line pressure (return to constant drive state).

To solve this problem many variations of the same theme were attemptedincluding auxiliary sources of force to operate the pivot linkages.

It was obvious from the above discussion that the sense roller and thesupport rollers could not be interconnected and that the linkage must bebroken.

A solution was found to this problem. The support rollers were fixedmounted. They were made with a flat side and the rollers were stoppedand with the flat side up to lower the drive belt. This itselfintroduced problem of noise and sluggish response. Each roller had astop pin which could be engaged by a linkage connected to the senseroller. As every package passed over each sense roller each pressureroller was stopped. This produces an undesirable noise level. The rollerstops with the belt lowered the only force exerted on the rollerattempting to start it when released was the belt weight. This wouldeventually start the roller but response was sluggish.

Further still, when the disengaged belt portion in the stopped zone isbrought back into driving engagement with the rollers in that zone, thedisplacement characteristics of the belt do not assure immediate maximumuniformvdriving of all the rollers in that zone and thus anotherminimization of efficiency arises from not utilizing uniform drive ofall the rollers.

This system was an improvement of the first designs, but it was stillnot sensitive to light loads because a certain amount of force wasrequired to disengage the linkage from the roller still under some powerin the stop position.

The principal object of the present invention is to eliminate theaforementioned disadvantages of conventional accumulator type conveyorsand to provide a conveyor of this type which is highly efficient inoperation, simple in construction, and adaptable to economicalmanufacture. This object is attained by providing each zone of theconveyor with a separate driving belt which constantly engages thetransport rollers in that zone, even when the belt and the rollers arestationary. The several driving belts are independently propelled byseparate driving means from a common drive source such as a main drivingbelt which extends over the several zones of the conveyor, the separatedriving roller in one zone, the clutch disengages the drive to thetransport roller driving belt in the next preceding or upstream zone andthe transport rollers in that zone cease to be driven although theirdriving belt still remains in engagement therewith.

The advantages of this arrangement are manifold. First, it is notnecessary to provide means for deflecting a portion of a long drivingbelt in and out of engagement with transport rollers in individualzones, and thus complicated belt deflecting means used in the prior artare eliminated. Second, by avoiding belt deflection or shifting, theinvention safeguards against the possibility of some transport rollersbeing driven when they should not be, or not being driven when theyshould be. In the same context, by providing a separate driving belt forthe transport rollers in each zone and maintaining that belt inengagement with these rollers at all times, the invention assures thatall the transport rollers in each zone are either uniformly driven or ata standstill Also, the use ofa mechanical clutch in the belt drivingmeans of each zone is a much simpler and more effective expedient thanthat of shifting portions of a long belt in and out of engagement withtransport rollers in the different zones, because its operation does notproduce an undesirable noise level and because its operation can be madesensitive to a light load and quickly responsive to activation.

With the foregoing more important object and features of the inventionin view and such other objects and features which may become apparent asthis specification proceeds, the invention will be understood from thefollowing description taken in conjunction with the accompanyingdrawings, in which like characters of reference are used to designatelike parts, and in which:

FIG. 1 is a fragmentary longitudinal sectional view of a conveyor inaccordance with the invention;

FIG. 2 is a fragmentary plan view thereof with certain parts brokenaway; I

FIG. 3 is a fragmentary sectional detail, taken substantially in theplane of the line 33 in FIG. 2;

FIG. 4 is an elevational view on an enlarged scale of one of the drivingsheaves;

FIG. 5 is a fragmentary sectional view, taken substantially in the planeof the line 55 in FIG. 4; and

FIG. 6 is a fragmentary perspective view of one of the driving rollerswith its clutch detent.

Referring now to the accompanying drawings in detail, the accumulatortype live roller conveyor of the invention is designated generally bythe reference numeral l0 and, as shown in FIGS. 1 and 2, it comprises anelongated supporting frame 12 which is suitably fabricated from angleiron and strap iron components either welded or bolted together. Thedetailed structure of the frame need not be described, but it is to benoted that it includes a pair of longitudinal side members 13 which aretransversely spaced and connected together by cross braces 14.Conveniently, the side members 13 may consist of opposing channels ofthe cross-section shown in FIG. 3.

The article supporting and transporting bed of the conveyor isconstituted by rotatable rollers arranged in groups so that the overalllength of the conveyor bed is divided into a plurality of successivezones, each of which may be two or three feet long. The conveyorstructure in each zone is the same, and thus a description of thestructural arrangement in one zone will suffice for all.

The longitudinal span of one zone is indicated at Z-l in FIG. 1 and thearticle supporting and transporting bed of the conveyor spanned by theone zone is constituted by a group of transport rollers 15 which arepositively driven, a sensing roller 16 which is located at thedownstream end of the group of rollers 15, and an idler roller 17 whichfills up space between the leading roller 15 in the group and thesensing roller 16 in the next preceding or upstream conveyor zone. Inthis regard it may be noted that the flow of articles on the conveyor isin the direction of the arrow 18 in FIG. 1 so that in relation to thezone Z-l there is a next preceding or upstream zone Z-2. Conversely, inrelation to the zone Z-2, there is a next following or downstream zoneZ-l. In the same context, in relation to the zone Z-l, there is a nextfollowing or downstream zone Z-3.

The rollers 15 and 17 extend transversely across the full width of theconveyor bed and are rotatably journalled in upper flanges of thechannel-shaped side members 13 so that all these rollers are disposed ina common plane. The sensing roller 16 is rotatably supported at its endsby a pair of bell cranks 19 which are pivoted as at 20 to the upperflanges of the side members 13, so that by rocking of the bell cranks ontheir pivots, the sensing roller 16 may be raised or lowered.Ordinarily, the roller 16 is in a raised position above the common planeor level of the rollers 15, 17, but is depressible to the level of theother rollers when an article on the conveyor passes Over the sensingroller. Suitable springs 21 react between the bell cranks l9 and theconveyor frame to bias the sensing roller to its raised position,although these springs may be omitted and the bell cranks becounter-weighted to attain the same result.

The two bell cranks 19 at the opposite ends of the sensing roller 16 arepivoted as at 20 to the two frame side members 13 as already mentioned,and simultaneous rocking movement of the bell cranks is assured byrigidly connecting their lower end portions together by a brace 19a.

The transport rollers 15 are positively driven by an endless belt 23which constantly engages the underside of these rollers and is trainedover a set of sheaves including a driving sheave 24 at one end, an idlersheave 25 at the other end, and intermediate idler sheaves 26. The belt23 and its sheaves are located only at one side of the conveyor, thesheaves being rotatably mounted on suitable brackets such as for examplethe brackets 27, secured to the inside of one of the frame side members13. The sheaves 25 and 26 assure that the upper run of the belt 23 isalways in contact with the underside of the transport rollers 15.Preferably, the driving sheave 24 is larger in diameter than the sheave25, so that the intermediate sheaves 26 supportably engage only theupper run of the belt. When the bell cranks 19 are moved in thedirection of the arrow 28 by passage 7 of an article on the conveyorover the sensing roller 16, the sensing roller is depressed to thecommon level of the rollers 15, 17 and in that position the sensingroller comes into contact with the driving belt 23 so that like thetransport rollers 15, the sensing roller is positively driven andassists in propelling the article into the next following or downstreamzone of the conveyor, as for example from the zone Z-l into the zoneZ-3, over the idler roller 17.

The driving sheave 24 is disposed adjacent one end of and coaxially witha driving roller 29, the latter having a supporting shaft which ismounted in the conveyor frame and which projects from one end of theroller 29 to also support the driving sheave. As is best shown in FIG.5, the driving sheave 24 is provided integrally with a hub 24' andsuitable anti-friction bearings 31 are provided in the sheave and hubfor mounting thereof on the projecting portion of the shaft 30 of theroller 29, which facilitates rotation of the roller'29 independently ofthe sheave 24.

As shown in FIGS. 4-6, the end portion of the roller 29 adjacent thesheave 24 has rigidly secured thereto a sleeve 32 which extends over thesheave hub 24 and is cut away as at 32 to form a semi-tubular detent 33which constitutes a component of a clutch now to be described. Thedetent 33 cooperates with another clutch component in the form of a pawl34 which is pivotally mounted on a pin 35 in a recess 36 formed in thesheave hub 24'. The pawl 34, being carried by the sheave hub 24', isspring-biased by a compression spring 37 to what may be referred to asits projected position in which the pawl abuts a stop pin 38 in thesheave hub, with a portion of the pawl projecting outwardly beyond thecircumference of the hub as shown in FIG. 4. The recessed portion of thesheave hub in which the pawl 34 is disposed is overlapped by thesemi-tubular detent 33 of the driving roller 29, the arrangement beingsuch that when the pawl is in its projccted position it engages thedetent and rotation of the roller 29 is transmitted through the clutchcomponents 33, 34 to rotate the sheave 24. However, when the pawl 34 isretracted against the action of the spring 37 into the recess 36 in thesheave hub 24, the clutch components are disengaged and rotation of thedriving roller 29 with the detent 33 may continue while the sheave 24remains stationary.

The clutch control mechanism comprises a push rod 39, one end portion ofwhich is slidable in a bracket 40 affixed to the frame, that end portionof the push rod having an upturned extension 39a which is disposed inclose relationship to the sheave hub 24' for cooperation with the pawl34. The other end of the push rod 39 is connected as at 41 to the bellcrank 19 of the next following or downstream zone. Thus for example, thepush rod 39 which has its portion 39a adjacent the sheave hub 24' in theconveyor zone Z-2 has its other end connected at 41 to the bell crank 19in the zone Z- 1. In this manner, when the sensing roller 16, forexample in the zone Z-l is depressed by passage of an article thereover,its depression is translated by rocking movement of the bell crank 19 inzone Z-l to slide the push rod 39 in zone Z-I rearwardly in thedirection of the arrow 42 for disengaging the clutch drive between theroller 29 and the sheave 24 in the next preceding or upstream zone Z-2.The clutch disengagement occurs when the rod 39 is slid rearwardly sothat its portion 39a contacts the pawl 34 and presses it into the hubrecess 36, whereby the pawl is retracted from its engagement with thedetent 33 and the roller 29 may continue to rotate while the sheave 24is stationary. Of course, when the push rod 39 returns to its initialposition, which is that in which the sensing roller 16 in the nextfollowing or downstream zone is raised, the rod portion 39 a moves awayfrom the sheave hub 24' and the pawl 34 is projected by the spring 37into engagement with the detent 33, thus establishing drive from theroller 29 to the sheave 24.

It may be noted that the parts are so proportioned that in the axialdirection, the detent 33 extends only over a portion of the width ofthepawl 34, thus leaving the remaining portion of the pawl unobstructed forcontact by the push rod portion 39a, without interfering with the detent33.

The roller 29 is positively and constantly driven by a main driving belt43 which passes over rollers 44 rotatably mounted between the lowerflanges of the frame side members 13. The rollers 44 support the belt 43and also sustain it in driving engagement with the underside of thedrive roller 29 in each of the several zones, it being understood thatthe main driving belt 43 is sufficiently long to span all the zones ofthe conveyor for constant driving of the rollers 29 in the severalzones.

In operation, the main driving belt 43 constantly drives all the drivingrollers 29 in the several zones of the conveyor and with the sensingrollers 16 and the clutches 33, 34 engaged, the driving sheaves 24rotate with the rollers 29. Ineach individual zone the driving sheave 24propels the driving belt 23 which is in constant contact with thetransport rollers 15 and, as long as the belt 23 is propelled, therollers 15 are rotated so as to transport an article through that zone,as for example the zone Z-l. In the meantime, other articles may be intransport through other zones of the conveyor, as for example the zoneZ-2.

When the article in zone Z-I passes over the sensing roller 16 on itsway into the next following zone C-3, the sensing roller is depressed.This, through the medium of the bell crank 19 and push rod 39 in zoneZ-l disengages the clutch drive between the roller 29 and the sheave 24driving the transport roller belt 23 in the next proceding zone Z-2, sothat the transport rollers 15 in the zone C-2 are stopped and furthermovement of the article through the zone C-2 is arrested until thearticle in zone C-l has cleared the sensing roller 16 and has passedinto the zone C-3.

It will be apparent that in this manner an article must pass through onezone before an article in the next preceding or upstream zone may enterthat one zone. Consequently, when an article is accidentally orintentionally stopped at any point along the length of the conveyor, allother articles behind it are also stopped at spaced apart distancescorresponding to the several zones of the conveyor, and piling of suchother articles against the stopped article is automatically prevented.As such, several articles may accumulate in the respective zones of theconveyor at a standstill and without piping up, until the initiallystopped article has resumed its movement.

It is to be particularly noted that the disengageable drive of thetransport rollers in the several conveyor zones is effected without thenecessity of shifting a belt in and out of driving engagement with therollers, as is customary in the prior art. Thus, the main driving belt43 is always in contact with and drives the rollers 29 in the severalconveyor zones. In each zone, the driving ticular zone is to bediscontinued, the drive to the beltv 23 in that zone is stopped bydisengagement of the associated clutch components 33, 34, while thedriving roller 29 still continues in its rotation. The constantengagement of the driving belt 23 with the transport rollers in eachzone assures that all the transport rollers in that zone are eitheruniformly rotating or at a standstill all without regard to driving ornon-driving of transport rollers in the adjacent zones. As indicatedearlier, an optimum situation such as this is difficult and oftenimpossible to attain with belt shifting arrangements of the prior art.

While in the foregoing there has been described and shown the preferredembodiment of the invention, various modifications and equivalents maybe resorted to within the spirit and scope of the invention as claimed.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. In an accumulating type live roller conveyor, the combination ofseveral groups of transport rollers, a depressible sensing rollerbetween every two adjacent groups of transport rollers, said transportrollers and sensing rollers constituting an article supporting bed whichis divided into a plurality of successive zones each containing onegroup of transport rollers and one sensing roller, a plurality ofdriving belts each constantly engaging the group of transport rollers inthe respective zones, a common drive source, separate driving meansindependently propelling the respective driving belts from said commondrive source, and control means responsive to depression of the sensingroller in each zone by passage of an article thereover, said controlmeans in each zone being operative to disengage the driving means in apreceding zone so that the driving belt in the preceding zone is stoppeduntil the depressed roller in the following zone is raised after passageof an article thereover.

2. The conveyor as defined in claim 1 which is further characterized inthat the sensing roller in each zone, when depressed engages the drivingbelt of that zone.

3. The conveyor as defined in claim 1 wherein each zone includes a setof sheaves including a driving sheave having the driving belt of thatzone trained thereover, said separate driving means including clutchmeans operatively connecting said driving sheave to said common drivesource, said control means being operative to disengage said clutchmeans when the sensing roller in the following zone is depressed.

4. The conveyor as defined in claim 3 wherein said separate drivingmeans in each zone also includes a driving roller continuously actuatedby said common drive source, said clutch means being operative betweensaid driving roller and said driving sheave.

5. The conveyor as defined in claim 4 wherein said common drive sourcecomprises a main driving belt extending over all the zones of saidarticle supporting bed, said main driving belt constantly engaging thedriving rollers in the respective zones.

6. The conveyor as defined in claim 1 wherein each zone includes a setof sheaves including a driving sheave having the driving belt of thatzone trained thereover, said common drive source comprising a maindriving belt extending over all the zones of said article supportingbed, and said separate driving means for each zone comprising a drivingroller continuously actuated by said main driving belt, and clutch meansoperatively connecting said driving sheave to said driving roller ineach zone, said control means being opera tive to disengage said clutchmeans when the sensing roller in the following zone is depressed.

7. The conveyor as defined in claim 6 which is further characterized inthat the sensing roller in each zone, when depressed engages the drivingbelt of that zone.

8. The conveyor as defined in claim 3 wherein each zone includes a setof sheaves including a driving sheave having the driving belt of thatzone trained thereover, said separate driving means for each zonecomprising a driving roller coaxial with said driving sheave andconstantly actuated by said common drive source, and clutch meansoperative between said driving roller and said driving sheave, saidclutchmeans including a projectable and retractable clutch membercarried by said driving sheave, and a cooperating detent carried by saiddriving roller and engaged by said clutch member when the latter isprojected, said control means being operative to retract and disengagesaid clutch member from said detent when the sensing roller in thefollowing zone is depressed.

9. The conveyor as defined in claim 8 wherein said common drive sourcecomprises a main driving belt extending over all the zones of saidarticle supporting bed, said main driving belt constantly engaging thedriving rollers in the respective zones.

10. The conveyor as defined in claim 8 wherein said control means ineach zone includes a push rod having one end portion thereof disposedadjacent said driving sheave of that zone for retracting said clutchmember, the other end of said push rod being operatively connected tothe sensing roller of the following zone.

11. In an accumulating type live roller conveyor, the combination of anelongated supporting frame, several groups of transport rollersrotatably journalled in said frame, a sensing roller depressibly mountedin the frame between every two adjacent groups of transport rollers andbiased to a raised position above the level of the transport rollers,said transport rollers and sensing rollers constituting an articlesupporting bed which is divided into a plurality of successive zoneseach containing one group of transport rollers and one sensing rollerfollowing the transport rollers in the direction of conveyor movement, aplurality of driving belts each constantly engaging the underside of thegroup of transport rollers in the respective zones, each zone includinga set of sheaves including a driving sheave rotatably mounted in saidframe and having the driving belt of that zone trained thereover,separate driving means for the driving sheave in each zone, said drivingmeans including a driving roller rotatable in said frame coaxially withthe driving sheave, and clutch means operative between said drivingroller and the driving sheave, a common drive source comprising a maindriving belt extending in said frame over all the zones of said articlesupporting bed and constantly engaging the underside of the drivingrollers in the respective zones,

and control means responsive to depression of the sensing roller in eachzone by passage of an article thereover, said control means in each zonebeing operative to disengage said clutch means in a preceding 7 sheave,and a cooperating detent carried by said driving roller and engaged bysaid clutch member when the latter is projected, said control meansbeing operative to retract and disengage said clutch member from saiddetent when the sensing roller in the following zone is depressed.

14. The conveyor as defined in claim 13 wherein said control means ineach zone includes a push rod having one end portion thereof disposedadjacent said driving sheave of that zone for retracting said clutchmember, the other end of said push rod being operatively connected tothe sensing roller of the following zone.

1. In an accumulating type live roller conveyor, the combination ofseveral groups of transport rollers, a depressible sensing rollerbetween every two adjacent groups of transport rollers, said transportrollers and sensing rollers constituting an article supporting bed whichis divided into a plurality of successive zones each containing onegroup of transport rollers and one sensing roller, a plurality ofdriving belts each constantly engaging the group of transport rollers inthe respective zones, a common drive source, separate driving meansindependently propelling the respective driving belts from said commondrive source, and control means responsive to depression of the sensingroller in each zone by passage of an article thereover, said controlmeans in each zone being operative to disengage the driving means in apreceding zone so that the driving belt in the preceding zone is stoppeduntil the depressed roller in the following zone is raised after passageof an article thereover.
 1. In an accumulating type live rollerconveyor, the combination of several groups of transport rollers, adepressible sensing roller between every two adjacent groups oftransport rollers, said transport rollers and sensing rollersconstituting an article supporting bed which is divided into a pluralityof successive zones each containing one group of transport rollers andone sensing roller, a plurality of driving belts each constantlyengaging the group of transport rollers in the respective zones, acommon drive source, separate driving means independently propelling therespective driving belts from said common drive source, and controlmeans responsive to depression of the sensing roller in each zone bypassage of an article thereover, said control means in each zone beingoperative to disengage the driving means in a preceding zone so that thedriving belt in the preceding zone is stopped until the depressed rollerin the following zone is raised after passage of an article thereover.2. The conveyor as defined in claim 1 which is further characterized inthat the sensing roller in eAch zone, when depressed engages the drivingbelt of that zone.
 3. The conveyor as defined in claim 1 wherein eachzone includes a set of sheaves including a driving sheave having thedriving belt of that zone trained thereover, said separate driving meansincluding clutch means operatively connecting said driving sheave tosaid common drive source, said control means being operative todisengage said clutch means when the sensing roller in the followingzone is depressed.
 4. The conveyor as defined in claim 3 wherein saidseparate driving means in each zone also includes a driving rollercontinuously actuated by said common drive source, said clutch meansbeing operative between said driving roller and said driving sheave. 5.The conveyor as defined in claim 4 wherein said common drive sourcecomprises a main driving belt extending over all the zones of saidarticle supporting bed, said main driving belt constantly engaging thedriving rollers in the respective zones.
 6. The conveyor as defined inclaim 1 wherein each zone includes a set of sheaves including a drivingsheave having the driving belt of that zone trained thereover, saidcommon drive source comprising a main driving belt extending over allthe zones of said article supporting bed, and said separate drivingmeans for each zone comprising a driving roller continuously actuated bysaid main driving belt, and clutch means operatively connecting saiddriving sheave to said driving roller in each zone, said control meansbeing operative to disengage said clutch means when the sensing rollerin the following zone is depressed.
 7. The conveyor as defined in claim6 which is further characterized in that the sensing roller in eachzone, when depressed engages the driving belt of that zone.
 8. Theconveyor as defined in claim 3 wherein each zone includes a set ofsheaves including a driving sheave having the driving belt of that zonetrained thereover, said separate driving means for each zone comprisinga driving roller coaxial with said driving sheave and constantlyactuated by said common drive source, and clutch means operative betweensaid driving roller and said driving sheave, said clutch means includinga projectable and retractable clutch member carried by said drivingsheave, and a cooperating detent carried by said driving roller andengaged by said clutch member when the latter is projected, said controlmeans being operative to retract and disengage said clutch member fromsaid detent when the sensing roller in the following zone is depressed.9. The conveyor as defined in claim 8 wherein said common drive sourcecomprises a main driving belt extending over all the zones of saidarticle supporting bed, said main driving belt constantly engaging thedriving rollers in the respective zones.
 10. The conveyor as defined inclaim 8 wherein said control means in each zone includes a push rodhaving one end portion thereof disposed adjacent said driving sheave ofthat zone for retracting said clutch member, the other end of said pushrod being operatively connected to the sensing roller of the followingzone.
 11. In an accumulating type live roller conveyor, the combinationof an elongated supporting frame, several groups of transport rollersrotatably journalled in said frame, a sensing roller depressibly mountedin the frame between every two adjacent groups of transport rollers andbiased to a raised position above the level of the transport rollers,said transport rollers and sensing rollers constituting an articlesupporting bed which is divided into a plurality of successive zoneseach containing one group of transport rollers and one sensing rollerfollowing the transport rollers in the direction of conveyor movement, aplurality of driving belts each constantly engaging the underside of thegroup of transport rollers in the respective zones, each zone includinga set of sheaves including a driving sheave rotatably mounted in saidframe and having the driving belt of that zone trained thEreover,separate driving means for the driving sheave in each zone, said drivingmeans including a driving roller rotatable in said frame coaxially withthe driving sheave, and clutch means operative between said drivingroller and the driving sheave, a common drive source comprising a maindriving belt extending in said frame over all the zones of said articlesupporting bed and constantly engaging the underside of the drivingrollers in the respective zones, and control means responsive todepression of the sensing roller in each zone by passage of an articlethereover, said control means in each zone being operative to disengagesaid clutch means in a preceding zone so that the driving belt in thepreceding zone is stopped until the depressed roller in the followingzone is raised after passage of an article thereover.
 12. The conveyoras defined in claim 11 which is further characterized in that thesensing roller in each zone, when depressed engages the driving belt ofthat zone.
 13. The conveyor as defined in claim 11 wherein the clutchmeans of each zone includes a projectable and retractable clutch membercarried by said driving sheave, and a cooperating detent carried by saiddriving roller and engaged by said clutch member when the latter isprojected, said control means being operative to retract and disengagesaid clutch member from said detent when the sensing roller in thefollowing zone is depressed.